Device and process for supplying respiratory gas under pressure or volumetrically

ABSTRACT

A device for supplying respiratory gas to a patient according to respiratory cycles, includes a gaseous flow rate generator provided with a turbine with low inertia and high nominal speed, a first supply circuit for the gaseous flow toward a respiratory mask or an intubation elements of the patient, elements for measuring pressure and/or measuring flow rate of the gaseous flow, the computation elements for parameters of pressure and/or flow rate, and elements for controlling the speed of rotation of the generator. The measuring elements, the computation elements and the speed control elements coact automatically to control the speed of rotation of the turbine as a function of the inspiration and expiration phases and as a function of patient pressure signals and/or inspiration flow rate signals.

The present invention relates to a device and process for supplyingrespiratory gas.

Devices for supplying respiratory gas are used particularly in thetreatment of respiratory ailments of adult or infant patients.

Such devices are adapted to supply a quantity of air, if desired withadded oxygen, either in the form of a quantified breathable volume, orin the form of a first predetermined pressure called inspirationpressure and a second predetermined pressure called expiration pressure.

WO 00/24447 relates to a device for supplying respiratory gas providedwith a compressor delivering a flow of gas under pressure to a patientthrough a downstream accumulator/silencer and a flow rate regulatingvalve. According to this document, the surplus of unneeded gas isreturned to an upstream filter/accumulator through a bypass valve so asto limit the loss of respiratory gas.

FR 2 663 547 A1 relates to apparatus for continuously providing anoverpressure of respiratory gas; this apparatus using a high speedturbine supplying gas under constant predetermined pressure regulated bymeasuring the pressure at the respiratory mask of the patient. Thisapparatus is passive in that the pressure is maintained continuously,the expiration phases being possible thanks to a calibrated loss at therespiratory mask of the patient.

FR 2 822 384 A1 in the name of the applicant relates to a mixedpulmonary ventilator provided with a flow generator, the circulationmeans permitting re-injecting the flow upstream of the generator duringan expiration phase of the patient, the circulation means comprisingparticularly a regulating valve comprising two flaps actuated by thesame actuator permitting several modes of regulation and an optimizationof the flow as a function of the inspiration and expiration phases.According to this document, the speed of rotation of the generator ismaintained constant, the pressure in the patient circuit beingcontrolled by the two flaps which permit return of the gas to thegenerator particularly during the expiration phases.

It remains that the circuits and systems necessary to provide and toregulate the levels of pressure and/or volumetric quantities ofrespiratory gas, are complicated and cumbersome, the control of theflaps and valves being sensitive.

The present invention seeks to provide a device for supplyingrespiratory gas, that is improved in that its operation uses anautomatic control of the turbine for the inspiration and expirationphases and does not use a return system for gas upstream of the turbine,thereby simplifying the system, whilst permitting operation with asealed circuit at the respiratory mask or of the intubation device ofthe patient during the inspiration phases and the loss during theexpiration phases.

To this end, the present invention relates to a device for supplyingrespiratory gas to a patient according to respiratory cycles, comprisinga gas for a generator, a circuit for bringing the gaseous flow to arespiratory mask or intubation device of the patient, means formeasuring the pressure and/or for measuring the gaseous flow rate, meansfor computing the parameters of pressure and/or flow rate and controlmeans of the speed of rotation of the generator, in which device themeasuring means act on the speed control means through computer means soas automatically to control the speed of rotation of the turbine as afunction of the inspiration and expiration phases as a function ofpatient pressure signals and/or inspiration flow rate signals.

The pressure measuring means can particularly comprise a patientpressure sensor and/or an expiration valve pressure sensor.

The flow rate measuring means can particularly comprise an inspirationflow rate sensor disposed adjacent the outlet of the generator.

The flow rate measuring means can comprise an expiration flow ratesensor in a patient return circuit.

In a particular embodiment, the device can comprise a passive member forgenerating a pressure drop in the supply circuit. This passive membercan particularly be a non-return flap if desired associated with apassive flap for admission of external air downstream of the non-returnflap in the supply circuit.

According to a particular embodiment of the invention, the devicecomprises an expiration circuit provided with an expiration valve and aproportional electro-valve for controlling said expiration valve byapplication of a counter-pressure.

The invention relates moreover to a process for providing a respiratorygas according to respiratory cycles, comprising inspiration andexpiration phases, according to which said measurement means and saidcomputing means act on said speed control means so as automatically tocontrol the speed of rotation of the turbine as a function of thepressure and/or volume standards, of the detection of the inspirationand expiration phases, of patient pressure signals and/or inspirationflow rate signals, the supply of the respiratory gas taking place as topressure or as to volume.

The process can preferably comprise phases of pressure increase withpressure increase slopes effected by acceleration of the turbine.

More particularly, the transition between an inspiration phase and anexpiration phase can be effected by controlled deceleration of theturbine.

The process can comprise, during expiration phases, a control of anexpiration valve with a pressure regulating member of the first circuit,via a proportional electro-valve which is part of a second circuit, thevalve being a part of a third circuit connected to the mask or to theintubation device.

Preferably, the computing means and the control means of the speed ofrotation of the generator can adapt the speed of the turbine as afunction of an expiration pressure threshold beyond a regulated loss bythe expiration valve so as to create a rinsing flow rate in the firstcircuit.

More particularly, during insufflation phases corresponding to theinspiration phases, an expiration valve, which is a part of a thirdcircuit connected to the mask or to the intubation device, can becontrolled for following the pressure through a proportionalelectro-valve and a second circuit.

In a particular embodiment, the process can comprise a measurement ofexpiration flow rate and a measurement of inspiration flow rate.

Other advantages and characteristics of the invention will becomeapparent from a reading of the description which follows, of anon-limiting example of the invention, with reference to FIG. 1, whichis a schematic view of a device for supplying respiratory gas accordingto the invention.

The device 1 for supplying respiratory gas or ventilation deviceaccording to FIG. 1, comprises a generator 2 of gaseous flow providedwith a turbine 2 a of low inertia and high rated speed. This gaseousflow generator is disposed in a chamber 20, preceded by a filter 21 forambient air inlet, by an upstream and downstream sound deadening means22 and 23. The turbine 2a is for example a turbine with a maximum speedof rotation of the order of 50,000 rpm, adapted to supply a pressure of70 millibar above ambient and a flow rate of the order of 200 l/min.

The air flow generator, thus comprises a micro-turbine with low inertia,driven by an electric motor, controlled by a computer or a computermeans 9 so as to provide a wide range of flow rates and pressures.

At the outlet of the chamber 20, the generator is connected to a firstcircuit 3 called a circuit for supplying gaseous flow toward arespiratory mask 4 or a intubation device (not shown) of the patient.

The generator is controlled by control means 10 in the form of anelectronic control card connected to a supply 24 and to computer means 9in the form of an electronic card with a microprocessor provided withcontrol software and connected to a control interface 25 with a screenand a keyboard.

So as to control the operation of the device and to cause it to operate,the computer means are connected to means 5, 6, 7, 8 for measuring thepressure and/or for measuring the flow rate of the gaseous flow in theform of sensors.

The sensor 6 is a pressure sensor connected to a first circuit 3 whichis a circuit for supplying gas to the mask 4 or intubation device of thepatient.

According to the example, a sensor 6 is disposed in the apparatus 1 andconnected to the mask 4 or to the intubation device via a tube 6 a.

The sensor 5 is a pressure sensor connected to a second circuit 16comprising a proportional electro-valve 15 whose operation will bedescribed later.

The sensor 7 is an inspiration flow rate sensor disposed in the firstcircuit, in a laminator 26 controlling the flow of gas leaving thegenerator.

An expiration flow rate sensor 8, in the third circuit 11 called patientreturn circuit, completes the measurement means.

The computation means 9 controls the members such as the generator andthe proportional electro-valve 15 as a function of standards enteredinto the interface 25 as a function of the ventilation programs and as afunction of the pressure and/or flow rate parameters from the sensors.

According to the invention, the measuring means 5, 6, 7, 8, thecomputing means 9 and the speed control means 10 coact in the firstinstance automatically to control the speed of rotation of the turbine 2a as a function of the inspiration and expiration phases and as afunction of the patient pressure signals and/or inspiration flow ratesignals.

So as to regulate the output flow of the generator, the device accordingto FIG. 1 comprises a passive member 12 for generating a pressure dropin the supply circuit in the form of a non-return flap 12 mounted in thefirst circuit 3. Thanks to this member, the pressure on the generatorside is always slightly greater than the pressure in the circuit 3 onthe mask supply side or intubation device, which permits among otherthings a better regulation of the operation of the device.

Downstream of this non-return valve 12, the circuit 3 comprises apassive flap 13 for the admission of external air. This flap permitslimiting the inspiration force of the patient by spontaneous respirationthrough the machine when the latter is not in operation.

On the mask side 4 or the intubation device after the circuit 3 forsupplying gas, is located a third circuit 11 called an expirationcircuit. This expiration circuit comprises an expiration valve 14 with amembrane permitting opening a passage either directly to the exterior orthrough tubing 11a toward a laminator 27 and an air outlet 28.

To the valve 14 is connected the second circuit 16 provided withproportional electro-valve 15 of the three-way type. This electro-valve15 receives along a first path a pressure outlet of the generator,comprises a second path to vacuum and is connected by a third path tothe valve 14.

The electro-valve permits controlling the valve 14 by applying acounter-pressure which closes the valve or limits its opening such thatthe expiration pressure will remain higher than the pressure of thesecond circuit 16. To release the valve 14, the electro-valve iscontrolled such that the pressure of the generator will be blocked, thesecond path of the free air being placed in communication with the thirdpath.

Thus a controlled expiration device is constructed about the expirationvalve 14 controlled by the electro-valve valve 15 connected to the flowgenerator, this electro-valve valve 15 permitting sending a portion ofthe generated flow to the expiration valve so as to oppose its opening.

The proportional electro-valve 15 is controlled by control means coupledto the computation means 9 and according to the example disposed on thecard receiving the computing means 9.

This device thus permits in operation, the control of the speed of theturbine 2 a and the control of the expiration valve through theelectro-valve to provide several modes of operation and particularlymodes of volumetric operation. Thus several modes of operation aresought and particularly modes of operation with inspiration andexpiration pressure standards or modes for which a volume of air calleda target volume is predetermined, or mixed modes.

The operation of the apparatus is based on a system of self-adaptivecontrol in a closed loop, of the speed of the flow generator. With thisflow generator is associated a controlled expiration device, without amember for regulation of the supplemental principal flow.

In particular, the detection of an increasing slope of pressure can betranslated by a level of acceleration of the turbine 2 a and thedetection of the transition between the inspiration phase and theexpiration phase can be translated by a deceleration of the turbine 2 a.

This control is effected by inspiration pressure or flow rate signalsand according to control laws, based on proportional and integralcoefficients, which differ according to the modes of ventilation, theadjustments of the pressure or flow rate and in particular the phases ofthe respiratory cycle.

The operation of the device and the associated ventilation process willbe explained for example in the case of a mode in which an inspirationpressure Pi, an expiration pressure Pe as well as a form of obtainingthe inspiration pressure based on the time of pressure increase, arefixed. The time of insufflation is here dependent on a level oftriggering the expiration adjusted on the basis of the measurement of adrop in flow rate measured in the inspiration detector 7, afterobtaining a maximum insufflation flow rate available for the patient.

A limiting parameter for the time of insufflation is the minimumthreshold corresponding to the slope of pressure measured; anotherparameter is a maximum threshold of safety for the insufflation timewhich corresponds to the last inspiration time carried out or at most tothree seconds. Other safety parameters can be taken into account such asa safety frequency.

According to this embodiment, the objective of the insufflation phase isthe establishment of a pressure level Pi with a variable time ofincrease and a holding time depending on the behavior of the associatedflow rate.

The objective of the expiration phase is to maintain a pressure level Peup to the beginning of the following inspiration phase, but alsosufficiently to rinse the circuit so as to evacuate the residual expiredgases.

To carry out inspiration cycles, the phases of pressure increase withincreased slopes of pressure are carried out by an acceleration of theturbine 2 a. The pressure is controlled in the inspiration pressuresensor 6.

During the insufflation phase corresponding to the inspiration phase,the computation means control the expiration valve 14, which is part ofthe third circuit 11 connected to the mask 4 or to the intubationdevice, via the proportional electro-valve 15 and the second circuit 16,according to pressure.

The transition between an inspiration phase and an expiration phase iseffected itself by a controlled deceleration of the turbine 2 a and theexpiration valve 14, which is part of the third circuit 11 connected tothe mask 4 or to the intubation device, is controlled, through theproportional electro-valve 15 and the second circuit 16, with a pressureregulation member of the first circuit 3.

During the expiration phase, the computation means and the means forcontrolling the speed of rotation of the generator adapt the speed ofthe turbine 2 as a function of an expiration pressure threshold beyond aloss regulated by the expiration valve 14 so as to create the rinsingflow rate of the first circuit.

The non-return clapet system 12 and the spontaneous respiration clapet13 permit balancing the rinsing pressure which is maintainedsufficiently low to limit the phenomenon of expiration braking withoutbeing canceled to avoid all heating of the turbine 2 a.

In the case of ventilation for which a current volume as well as afrequency and a cycling ratio are fixed, the objective of theinsufflation phase is the distribution of a current volume Vt with asuitable flow rate shape and during a time fixed by the frequency levelsand the ratio of cycling regulated by the interface 25.

In this case, during insufflation, the patient current comprising thecircuit 3, the mask 4 or intubation device is maintained sealed, againstparasitic loss by the closing of the valve 14 controlled by theelectro-valve 15. As a result, there is an increase in pressure of thecircuit 3 and of the pulmonary system of the patient depending on thecharacteristics of the patient. In the case of exceeding the objectiveof maximum pressure measured with the pressure sensor 6, it is possibleto cause the pressure in the control circuit 16 of the valve 14 by acommand of the electro-valve 15 and to pass immediately into theexpiration phase.

In the case of a target volume mode, the operator enters by theinterface means a target volume standard into the computation means 9which, as a function of this parameter and other parameters entered bythe interface such as the frequency of minimum cycle and/or safety,cycling ratio, high pressure threshold, will permanently adjust theinsufflation pressure between a low pressure threshold and a maximumpressure threshold so as to maintain the current volume inhaled by thepatient as nearly as possible to a predefined target volume, namely forexample between target volume Vt and target volume Vt+20%.

According to the target volume mode, it is particularly necessary to beable at the same time to adjust precisely the pressure by pressure stepsbetween the cycles. For example, for a pressure standard of the order of20 millibars, the steps between cycles are defined between 0.5 millibarand 2 millibars so as to react immediately to the detection of anunbalance without having a strong reaction that would be uncomfortableto the patient.

This pressure adjustment is made according to the invention without aregulator device such as the generator but by controlling the speed ofthe turbine 2 a of the generator 2 as a function of the pressuremeasurements of the sensor 6 of the pressure of the patient and bycausing to operate the expiration circuit comprising the expirationvalve 14 following through the proportional electro-valve 15 in which,in this configuration, the flow generator is connected to the secondcircuit, the non-return flap 12 of the first circuit 3 permittingpreserving a pressure slightly greater in the second circuit relative tothe first circuit.

Thus the device permits providing a respiratory gas according torespiratory cycles comprising phases of inspiration and expiration, themeasuring means 5, 6, 7, 8 and the computation means 9 acting on thespeed control means 10 so as automatically to control the speed ofrotation of the turbine 2 as a function of the pressure and/or volumestandards, of the detection of inspiration and expiration phases, ofpatient pressure signals and/or inspiration flow rate signals.

With the device of the invention, the expiration valve 14 is controlledby the pressure during the inspiration phase and by a regulating memberduring the expiration phase.

The device according to the invention thus permits ventilating a patientby pressure or volume with a patient circuit provided with an expirationdevice controlled by a simple control of the speed of the turbine.

1. Device (1) for supplying respiratory gas to a patient according torespiratory cycles, comprising a gas flow generator (2) provided with aturbine (2 a) with low inertia and high nominal speed, a first circuit(3) called a circuit for supplying a gaseous flow to a respiratory mask(4) or to an intubation means of the patient, means (5, 6, 7, 8) formeasuring the pressure and/or flow rate of the gaseous flow, means (9)for computing parameters of pressure and/or flow rates and means (10)for controlling speed of rotation of the generator, characterized inthat the measuring means (5, 6, 7, 8), the computation means (9) and themeans (10) for controlling the speed coact automatically to control thespeed of rotation of the turbine (2 a) as a function of the inspirationand expiration phases and as a function of the patient pressure signalsand/or inspiration flow rate signals.
 2. Device according to claim 1,characterized in that the pressure measuring means comprise a sensor (6)of patient pressure and/or a sensor (7) of expiration valve pressure. 3.Device according to claim 1, characterized din that the flow ratemeasuring means comprise a sensor (7) of inspiration flow rate disposedadjacent the outlet of the generator (2).
 4. Device according to claim1, characterized in that it comprises a passive member (12) forgeneration of a pressure drop in the supply circuit.
 5. Device accordingto claim 4, characterized in that this passive member (12) is anon-return flap if desired associated with a passive flap (13) for theaddition of external air downstream of the non-return flap in the supplycircuit (3).
 6. Device according to claim 1, characterized in that itcomprises a second circuit (16) comprising a proportional electro-valve(15), for controlling an expiration valve (14) that is part of a thirdcircuit (11) by application of a counter-pressure to this valve (14),control means of said proportional electro-valve (15) being coupled tothe computation means (9).
 7. Device according to claim 1, characterizedin that the means for measuring flow rate comprise an expiration flowrate sensor (8) in the third circuit (11) so-called patient returncircuit.
 8. Process for supplying a respiratory gas according torespiratory cycles, comprising inspiration and expiration phases, bymeans of a device according to claim 1, characterized in that themeasuring means (5, 6, 7, 8) and the computation means (9) act on thespeed control means (10) so as automatically to control the speed ofrotation of the turbine (2 a) as a function of pressure and/or volumestandards, of the detection of the inspiration and expiration phases, ofpatient pressure signals and/or inspiration flow rate signals, thesupplying of the respiratory gas taking place as to pressure and/or asto volume.
 9. Process according to claim 8, characterized in that itcomprises phases of pressure increase with increase slopes of pressureproduced by acceleration of the turbine (2 a).
 10. Process according toclaim 8, characterized in that the transition between an inspirationphase and an expiration phase is carried out by controlled decelerationof the turbine (2 a).
 11. Process according to claim 8, characterized inthat during expiration phases, an expiration valve (14) which is part ofa third circuit (11) connected to the mask (4) or to the incubationdevice, is controlled, via a proportional electro-valve (15) and asecond circuit (16), by a regulation member of the pressure in the firstcircuit (3).
 12. Process according to claim 11, characterized in thatthe computation means and the control means of the speed of rotation ofthe generator adapt the speed of the turbine (2 a) as a function of athreshold of this expiration pressure beyond a regulated loss, by theexpiration valve (14), so as to create a rinsing flow rate in the firstcircuit.
 13. Process according to claim 8, characterized in that duringphases of insufflation corresponding to the inspiration phases, anexpiration valve (14), which is part of a third circuit (11) connectedto the mask (4) or to the intubation device, is controlled via aproportional electro-valve (15) and by a second circuit (16), accordingto pressure.
 14. Process according to claim 8, characterized in that itcomprises a measurement of expiration flow rate and a measurement ofinspiration flow rate.
 15. Device (1) for providing a respiratory gas toa patient according to respiratory cycles, comprising a gas flowgenerator (2) provided with a turbine (2 a) for flow inertia and highnominal speed, a first circuit (3) called a circuit for supplyinggaseous flow toward a respiratory mask (4) or an intubation means of thepatient, means (5, 6, 7, 8) for measuring pressure and/or of flow rateof the gaseous flow, computation means (9) of parameters of pressureand/or flow rate, and means (10) for controlling the speed of rotationof the generator, characterized in that the measuring means (5, 6, 7,8), the computation means (9) and the speed control means (10) coactautomatically to control the speed of rotation of the turbine (2 a) as afunction of the inspiration and expiration phases and as a function ofthe patient pressure signals and/or inspiration flow rate signals, andin that the control system of the generator carries out phases ofpressure increase with increasing slopes of pressure by means ofacceleration of the turbine (2 a), the supply of respiratory gas takingplace according to pressure or according to volume.
 16. Device accordingto claim 15, characterized in that the control system of the generatorcarries out the transition between an inspiration phase and anexpiration phase by means of controlled deceleration of the turbine (2a).
 17. Device according to claim 15, characterized in that the controlsystem of the generator comprises means permanently adjusting theinsufflation pressure between a low pressure threshold and a maximumpressure threshold so as to maintain the inspiration current volume asnear as possible to a predetermined target volume.
 18. Device accordingto claim 15, characterized in that it comprises a proportionalelectro-valve (15), a second circuit (16) and an expiration valve (14),the proportional electro-valve (15) and the second circuit (16) beingarranged to control the expiration valve (14) with a pressure regulatingmember of the first circuit (3) during expiration phases.
 19. Deviceaccording to claim 15, characterized in that computation means and themeans for controlling the speed of rotation of the generator arearranged to adapt the speed of the turbine (2 a) as a function of anexpiration pressure threshold beyond a loss regulated by an expirationvalve (14) so as to create a rinsing flow rate in the first circuitduring expiration phases.
 20. Device according to claim 18,characterized in that the proportional electro-valve (15) and the secondcircuit (16) are arranged to control the expiration valve (14) accordingto pressure during insufflation phases corresponding to the inspirationphases.